An active matrix substrate used in a liquid crystal display device and the like includes a display region including a plurality of pixels, and a region other than the display region (a non-display region or a frame region). The display region includes a switching element such as a Thin Film Transistor (hereinafter referred to as a “TFT”) for each of the pixels. As such a switching element, a TFT including an amorphous silicon film serving as an active layer (hereinafter referred to as an “amorphous silicon TFT”) and a TFT including a polycrystalline silicon film serving as an active layer (hereinafter referred to as a “polycrystalline silicon TFT”) have been widely used in the related art.
The use of an oxide semiconductor as a material of the active layer of the TFT, in place of amorphous silicon and polycrystalline silicon has been proposed. Such a TFT is referred to as an “oxide semiconductor TFT.” The oxide semiconductor has mobility higher than mobility of amorphous silicon. Thus, the oxide semiconductor TFT can act at a higher speed than the amorphous silicon TFT.
In the non-display region of the active matrix substrate, a drive circuit such as a gate driver and a source driver may be provided in a monolithic manner (integrally). The drive circuit formed in a monolithic manner is called a “monolithic driver.” The monolithic driver is typically constituted by using a TFT. In recent years, a technique of preparing the monolithic driver by using the oxide semiconductor TFT has been used. Accordingly, cost reduction by narrowing of the non-display region and simplifying of a mounting process is achieved. In a device highly demanding narrowing of a frame, a gate driver circuit may be formed in a monolithic manner in the non-display region, and a source driver circuit may be mounted in the non-display region by a Chip On Glass (COG) method, for example.
A liquid crystal display device of an active matrix type is manufactured by providing a counter substrate to face the active matrix substrate described above, and enclosing a liquid crystal material in a space between these substrates, for example. The liquid crystal material is enclosed with a sealing member. The sealing member is disposed to surround a display region.
For example, PTL 1 discloses a liquid crystal display device of an active matrix type including a monolithic gate driver. In the display device disclosed in PTL 1, an output transistor constituting the gate driver is disposed closer to a display region than a sealing member, and another TFT and a capacitor constituting the gate driver are disposed to overlap with a region where the sealing member is applied. In PTL 1, an opening or a cut-out portion provided in a capacitor connected to a gate of the output transistor (a bootstrap capacitance portion) to facilitate an inspection step of the sealing member or to irradiate the sealing member with light when the sealing member being photocurable is used, has been proposed.